Aluminium extrusion billet · Alloy and diameter, length and straightness tolerances, casting and homogenising, extrusion and ageing guidance
An aluminium alloy extrusion billet is a cylindrical log of a heat-treatable alloy such as 6063 or 6061, direct-chill cast, homogenised and cut to length, which extruders preheat and press through a die. Ask three things first: which alloy and diameter you need and to what tolerances, how the billet was cast, degassed and homogenised, and what extrusion and ageing practice the billet maker recommends for your products.
Direct-chill cast and homogenised aluminium alloy logs and billets for extrusion and forging. Rolling slab, foundry ingot, machined bar stock and finished extrusions are outside this page.
CNFX editorial research · Sources checked October 12, 2026 · 4 sources
INALUM, Indonesia's aluminium smelter, produces 6xxx billet such as 6061 and 6063 in 5 in (127 mm ± 1 mm), 7 in (178 mm ± 2 mm) and 8 in (203 mm ± 2 mm) diameters, weighing about 198, 388 and 506 kg per billet. Billets are 5,800 mm ± 6 mm long, logs 1,001–6,000 mm ± 15 mm, with straightness of at most 1 mm per metre (6 mm over 5.8 m). [1]
TST's TANDEM operation supplies billet to extruders and forgers in diameters from 6 in to 43 in, with standard alloys including 2219, 2618, 6061, 7075/7175, 7050 and 7149 for extrusion. [2]
Editorial calculation: assuming a density of 2.70 g/cm³, a 127 mm × 5,800 mm billet weighs π/4 × 0.127² × 5.8 × 2,700 ≈ 198 kg, a 178 mm one about 390 kg and a 203 mm one about 507 kg — consistent with INALUM's listed weights, so weight per billet is a quick check on diameter and length. [1]
Give the supplier the alloy and composition limits, diameter and tolerance, billet or log length and tolerance, straightness, end-cut quality, homogenising requirement, quantities per month, packing and marking, inspection (chemistry, macro-etch, ultrasonic, hydrogen) and certificates.
02
Check casting, cleanliness, homogenising and ageing practice
INALUM describes vertical direct-chill casting with Hycast gas-cushion moulds to maximise separation of hydrogen and inclusions, an ABB electromagnetic stirrer for a more homogeneous product, and batch homogenising that lowers extrusion pressure and improves mechanical properties and processing. [1] TST passes all molten metal through its patented degassing process to keep hydrogen very low, uses dual ceramic foam filters, and monitors hydrogen and cleanliness through casting, homogenising, scalping and cutting. [2]
Rusal's data sheet for its 6063 MaxiFlow billet, designed for high-speed extrusion while meeting EN 755 6063-T66 strength, targets 0.47 wt% magnesium and asks for clean billet surfaces free of sand, mud and other foreign material to limit surface defects and die-bearing wear. It recommends natural ageing of 12–24 h (even 4 h helps) before artificial ageing at about 170–200 °C for 2–8 h, lower temperatures and longer times giving finer precipitation and higher strength, and the data sheet gives peak-aged properties of 250–260 MPa tensile, 230–240 MPa yield and 12% elongation on sections up to 3.2 mm. [3]
Editorial note: ask billet suppliers to back any cleanliness claim with measured hydrogen content, inclusion rating or filtration practice, and macro-etch or ultrasonic results on your alloy.
03
Check a second smelter's diameter list and geometric tolerances
Emirates Global Aluminium's product booklet (July 2026) says its extrusion and forging billets are cast with Airslip technology, ultrasound inspected and homogenised before delivery, with a large share of production in high-extrudability 6063 for windows, door frames, transport, engineering and forging. Billets are made in 1000, 3000 and 6000 series alloys to customer specifications, in diameters of 152, 155, 178, 203, 216, 228, 254, 273, 279, 305, 355, 381 and 406 mm with a diameter tolerance of +1 mm, and cut to lengths from 420 mm to 7,500 mm. Its geometric tolerances are a bow of 2 mm per metre of log length and a squareness of cut of 1 mm per 100 mm of diameter, or 0.5° maximum deviation. Bundles are steel- or plastic-strapped on wooden runners for fork-lift handling. [4]
Editorial calculation: at 2.70 g/cm³, a 406 mm billet 7,500 mm long weighs about 2,620 kg, against about 198 kg for INALUM's 127 mm × 5,800 mm billet. EGA's 2 mm/m bow limit is twice INALUM's ≤1 mm/m straightness, and its squareness rule allows about 2 mm out-of-square on a 203 mm cut. State diameter, tolerance direction (EGA quotes +1 mm; INALUM ±1 to ±2 mm), cut length, bow and squareness to suit your press container and billet loader. [4][1]
The listing reviewed describes alloy billet as the raw material for extruded profiles; ask for the alloy range, diameters, casting and homogenising route and certificates.
05
How chemistry, hydrogen and homogenising show up in the extrusion
Billet diameter and cut tolerances, then properties after ageing
Diameter, length and straightness come from INALUM and EGA; the strength figures apply to the extruded section after ageing, not to the billet, so ask for them against your own ageing practice.
Field
What it means and published values
Ask the supplier for
Diameter (mm)
Examples 127, 178, 203 mm; 152–406 mm; 6–43 in. [1][4][2]
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What diameters do extrusion billets come in?
INALUM lists 5, 7 and 8 in (127, 178, 203 mm); TST casts from 6 in to 43 in. [1][2]
What tolerances apply to extrusion billet?
INALUM gives ±1–2 mm on diameter, ±6 mm on 5,800 mm length and 1 mm per metre straightness. [1]
Why are billets homogenised?
INALUM says homogenising lowers extrusion pressure and improves mechanical properties and processing. [1]
What strength does 6063 billet reach after ageing?
Rusal lists 250–260 MPa tensile and 230–240 MPa yield peak-aged for its MaxiFlow types. [3]
What straightness and squareness tolerances apply to extrusion billet?
One smelter's booklet lists a bow of 2 mm per metre and cut squareness of 1 mm per 100 mm of diameter or 0.5°, with +1 mm diameter tolerance. [4]
Sources and what still needs a direct check
Sources checked 2026-10-12. INALUM, TST and Rusal are billet and aluminium producers describing their own products and practice; figures are their published values, not standard limits.
